Congenital Ewing's sarcoma of the humerus.

We report an extremely rare case of Ewing's sarcoma (ES) of the humerus in a Chinese neonate. Plain radiography and magnetic resonance imaging showed extensive neoplastic involvement of the humeral diaphysis and adjacent soft tissues, confirmed on histology and immunohistochemistry as being due to ES. This is the first report of congenital ES in a long bone. Since ultrasound at 20 weeks gestation showed a normal fetal skeleton, the ES may have begun to develop in the late middle or third trimester.